1. Field of the Invention
This invention relates to holder apparatus for transparencies and, more particularly, to a folder for holding a plurality of transparencies for sequential projection.
2. Description of the Prior Art
U.S. Pat. No. 3,709,590 (Bisberg) discloses a three-leaf folder for holding transparencies to be projected by an overhead projector. The leaves are hinged to a base element. The base element is disposed on the top surface of an overhead projector. The apparatus includes a support frame against which the transparencies may be disposed. Multiple transparencies may be projected, but the transparencies are overlays, and may accordingly may not be projected selectively individually.
U.S. Pat. No. 3,913,740 (Bisberg) discloses another folder for use with an overhead projector. The apparatus includes structure similar to that of the '590 Patent. The apparatus of the '740 Patent may be used with the apparatus of the '590 Patent. Both patents are by the same patentee. The apparatus includes four separate elements, connected together, with a base element and three elements secured to the sides of the base element. A plurality of transparencies is secured between two of the hinged elements.
U.S. Pat. No. 4,137,650 (Hayes) discloses a teaching aid for transparencies usable with an overhead projector. The apparatus includes a base element to which a number of transparencies are secured for sequential or individual projection. The base element includes four flaps foldable over the base element to define a container. The elements are hinged together to comprise a unitary structure.